What is the greatest question in all of epistemology?

The greatest question which is practically important to
all is "what do people know?".

Skepticism and fallibilism were treated as alternatives
until the advent of modern science. The subject of
sensors and measurements gave great insights into that
question.

Perception:

Mathematically speaking, perception is the integration of pieces information
provided by the senses.

http://www.gibson-design.com/philosophy/Concepts/$_PERCEPTION_1.html

The process of organizing information received through the senses and interpreting it. This is done by the conscious, mentally aware (faculty of) brain.

http://biotech.icmb.utexas.edu/search/dict-search2.html?bo1=AND&word=perception&search_type=normal&def=

Perception goes beyond plain sensation in that it includes the results of further processing of the sensed stimuli, either conceously or inconceously.

http://www.schorsch.com/kbase/glossary/perception.html

Recognition and interpretation of sensory stimuli based chiefly on memory.
The neurological processes by which such recognition and interpretation are effected.

http://www.thefreedictionary.com/perception

In psychology. and the cognitive sciences, perception is the process of acquiring, interpreting, selecting, and organizing sensory information. It is a task far more complex than was imagined in the 1950s and 1960s, when it was proclaimed that building perceiving machines would take about a decade, but, needless to say, that is still very far from reality. The word perception comes from the Latin perception-, percepio, , meaning "receiving, collecting, action of taking possession, apprehension with the mind or senses." (every moment).

Methods of studying perception range from essentially biological or physiological approaches, through psychological approaches through the philosophy of mind and in empiricist epistemology, such as that of David Hume, John Locke, George Berkeley, or as in Merleau Ponty's affirmation of perception as the basis of all science and knowledge.

http://en.wikipedia.org/wiki/Perception_%28psychology%29

The faculty of perceiving; the faculty, or peculiar part, of man's constitution by which he has knowledge through the medium or instrumentality of the bodily organs; the act of apperhending material objects or qualities through the senses; - distinguished from conception. (Sir W. Hamilton.)

in psychology, mental organization and interpretation of sensory information. The Gestalt psychologists studied extensively the ways in which people organize and select from the vast array of stimuli that are presented to them.

Perception is influenced by a variety of factors, including the intensity and physical dimensions of the stimulus; such activities of the sense organs as effects of preceding stimulation; the subject’s past experience; attention factors such as readiness to respond to a stimulus; and motivation and emotional state of the subject. Stimulus elements in visual organization form perceived patterns according to their nearness to each other, their similarity, the tendency for the subject to perceive complete figures, and the ability of the subject to distinguish important figures from background. Perceptual constancy is the tendency of a subject to interpret one object in the same manner, regardless of such variations as distance, angle of sight, or brightness. Through selective attention, the subject focuses on a limited number of stimuli, and ignores those that are considered less important.

http://www.bartleby.com/65/pe/percepti.html

Perception (psychology), process by which organisms interpret and organize sensation to produce a meaningful experience of the world. Sensation usually refers to the immediate, relatively unprocessed result of stimulation of sensory receptors in the eyes, ears, nose, tongue, or skin. Perception, on the other hand, better describes one’s ultimate experience of the world and typically involves further processing of sensory input.

http://encarta.msn.com/encnet/refpages/RefArticle.aspx?refid=761571997

The 'how it is' to cognitive systems in the world. A means of distinguishing how things are from how a cognizer thinks they are.

http://philosophy.uwaterloo.ca/MindDict/P.html

Awareness of an object of thought, especially that of apparently external objects through use of the senses. Since things don't always turn out actually to be as they seem to us, there is ample reason to wonder about the epistemological reliability of sense perception, and theories of perception offer a variety of responses. The skeptical challenge to direct realism is often answered by representative realism, phenomenalism, or idealism.

http://www.philosophypages.com/dy/p2.htm#perc

Our minds are as different as our finger prints -
no two are alike. The perception of one person is
bound to be different from that of another person
- the process used is designated by the word "conception".
Still, all those perceptions are interpretations of
the same reality.

"Our two minds .... One is an act of the emotional
mind, the other of the rational mind. In a very
real sense we have two minds, one that thinks and
one that feels" (Daniel Goleman, Emotional
Intelligence, Bloomsbury Publishing, London, 1996,
page 8). This rational mind is also called the
faculty of logic and reason. The rational mind
handles the conscious perceptions. However, the
logic used by the rational mind has a drawback.

In the 1930s, Austrian mathematician Godel proved a
theorem which became the "Godel theorem" in cognition
theory. It states that any formalized 'logical' system
in principle cannot be complete in itself. It means
that a statement can always be found that can be
neither disproved nor proved using the means of that
particular system. To discuss about such a statement,
one must go beyond that very logic system; otherwise
nothing but a vicious circle will result. Psychologist
say that any experience is contingent - it's opposite
is logically possible and hence should not be treated
as contradictory.

http://www.search.com/search?q=godel+incompleteness+theorem

The arguments permitted by the theorem gives rise to
many interpretations of the same reality.

The Upanishads say that even a the smallest thing
in creation, say a one cell organism, is a microcosm.
The more you try to know about it, you will understand
that there is more to know. Reality has infinite
dimensions. Perception is an approximate interpretation
of reality.

I would say that would be: "Does true knowledge exist?"

Can we really know anything, or are we merely knowing the shadows of the real, as in Plato's allegory of the cave? Can we really know what the essence of a triangle, or of a chair, is? Or is it on a higher plane? Can we really know who we are, or are we merely knowing the shadow we see in ourselves of the universal self? As you can see, this is essentially the fundamental question of epistemology, the nature of knowledge.

How do we know what we know, and how do we know that we know it?

"Why?"

What makes us more than animals?

"Long hair, short hair. What the hell's the difference once the head's blowed (sic) off."
National Lampoon, circa '73
;-)

Whose human ,spiritual,ethical knowledge of the world is right ? Western,Eastern or Indigenous cultures

Are we asking the right questions?

the best epistemological question would be:

why is it so fucking when you're having sex?